The present invention relates to a system for continuously injecting fuel into the intake line or pipe of an internal combustion engine. The system has an air channel branching off from the intake pipe ahead of an arbitrarily adjustable throttle flap. A fuel metering device supplies fuel to the air channel according to the engine load and a fuel delivery pump, supplying fuel to the injectors, receives fuel through a constriction or narrowed cross section in the channel.
One fuel injection system of this type is disclosed in the West German Patent No. 1,243,917. In this system fuel is supplied by a metering valve in proportion to the air passing into a chamber. A fuel injection pump is connected to receive fuel from this chamber via an inlet line and supplies the fuel, if necessary by way of a distributor, to a plurality of fuel injection nozzles arranged at the intake ducts associated with the several cylinders of the engine. The chamber into which the fuel is metered, and which is in communication with the intake pipe of the engine, has a substantially larger cross section than the inlet line of the injection or fuel delivery pump so that variations in volume flow through the pump cannot adversely affect the proportioning of fuel. In this system, the pump is designed to deliver substantially pure fuel under conditions of maximum engine load, and a mixture of air and fuel at small loads.
The advantage of this type of fuel injection system lies in its comparatively simple construction, since much of the precision apparatus involved in a conventional fuel injection system is avoided. However, the "preparation" of the fuel delivered, and also the responsiveness of such a fuel injection system to unsteady engine operating conditions, remain less than satisfactory. Since there is a comparatively low flow velocity in the chamber to which the fuel is supplied, because of the intended disassociation of this flow from the pressure fluctuations caused by the delivery pump, the time during which the fuel is transported from the moment of metering to the moment of injection is comparatively long. Therefore, the reaction time of the fuel injection system under rapidly changing engine operating conditions--with the resulting, corresponding variations in the fuel supply--is unacceptably slow.